The present invention is directed to a joint for transferring load from the underframe of a locomotive to the cant rail of the locomotive's car body. The joint includes a base connected to the underframe of the locomotive with a body portion attached thereto. This body portion carries a generally diagonally situated member connected to the cant rail of the car body of the locomotive, such that some of the load from the underframe is transferred to the base of the joint, through the body portion of the joint, to the diagonally situated member and to the cant rail during bending of the underframe of the locomotive. In another aspect of the present invention, the joint may be generally flexible to accommodate bending of the car body and underframe of the locomotive relative to their respective stiffness.
FIG. 1 illustrates a traditional locomotive. The locomotive's car body 102 is generally fixed and welded to an underframe 100 at 106 and welded to a cab 104 at 108. The underframe 100 and cab 104 are also welded together at 110. In this traditional arrangement, the underframe 100 is generally heavy; it may be between about 70,000 and about 100,000 pounds and is generally about 90,000 pounds. Accordingly, any bending of the underframe 100 is generally minimal and gradual.
However, in the course of operation, the traditional locomotive's engine transfers vibrations to any connected structures. These vibrations cause the panels of the cab structure to vibrate and contribute to an increase in noise level within the cab. In order to reduce the noise level in the cab structure, the cab may be supported on isolators. Locomotives with isolated cabs are preferable because, in addition to limiting noise, they limit shock vibrations in the cab.
In contrast to the traditional locomotive, the bending of the underframe of a locomotive with an isolated cab is not gradual and, because the underframe is generally light and flexible (between about 40,000 and about 50,000 pounds, generally about 45,000 pounds), it is easily bent. In a locomotive having an isolated cab 204, as shown in FIG. 2, or any other locomotive having a generally lighter and more flexible underframe 200, the locomotive operational loads transfer from the underframe 200 structure to the car body 202. In this arrangement, the cab 204 is isolated from the underframe 200 and the car body 202 (i.e. there is no welding between the cab 204 and underframe 200 and there is no welding between the cab 204 and the car body 202). Instead, the cab 204 includes isolators 208 (e.g., bushings or the like) which limit shock vibration in the cab 204. In this arrangement, the underframe 200 and car body 202 are welded and form a weld joint, which causes the underframe 200 and car body 202 to rotate together. The point of rotation 212 is at the point where the car body 202 and the underframe 200 meet behind the cab 204. Since the welding of these two structures will lead to the same rotational value, their different stiffness values will lead to high stress concentrations at the connection between them. As shown in FIG. 3, the rotational value θ for the underframe 300 and car body 302 is the same, causing high stress at the point of rotation 312. Accordingly, the portion of the underframe 300a connected to the isolated cab will bend more than the portion of the underframe 300b welded to the car body 302, thereby causing high stress to the underframe 300 at the point of rotation 312. One example of an isolated cab system is described in U.S. patent application Ser. No. 11/943,261, entitled “Cab Isolation System for a Locomotive,” the disclosure of which is incorporated by reference herein and made a part hereof.
Various attempts have been made to provide construction for a locomotive and underframe that provide the necessary strength and durability for the highly stressed portion of the car body. For example, a direct-bolted fastener has been used to attach the engine and generator directly to the underframe of the locomotive. Nevertheless, this arrangement has caused inordinate stresses in the engine bed and base structure, resulting at times in distortion, misalignment or deformation of the lower portions of the engine.
Therefore, in order to resolve the problem of force distribution, it is an aspect of the present invention to provide a joint to transfer some of the load from the underframe to the cant rail and transfer the remainder of load back through the underframe. In another aspect of the present invention, the joint may be generally flexible to enable the underframe and car body to rotate with different rotational values relative to their stiffness values. Since both structural components are allowed to rotate separately, the stress concentration problems have been resolved.